Samding Dorje Phagmo Losang Chö kyi Gyaltsen (Tibetan: བློ་བཟང་ཆོས་ཀྱི་རྒྱལ་མཚན་, Wylie: blo bzang chos kyi rgyal mtshan) (1570–1662) was the fourth Panchen Lama of the Gelug school of Tibetan Buddhism and the first to be accorded this title during his lifetime.

Losang Chö kyi Gyaltsen was the teacher and close ally of the 5th Dalai Lama, called "the Great".

[1] When Losang Chö kyi Gyaltsen died in 1662, aged 91 or 92, the Fifth Dalai Lama began the tradition of recognising his reincarnation.

He composed a special prayer asking his master to return and ordered the monks of the great monasteries to recite it.

He wrote a root Mahamudra text on the "Highway of the Conquerors: Root Verses for the Precious Geden [Gelug] Kagyu [Oral] Transmission of Mahāmudrā" (dGe-ldan bka'-brgyud rin-po-che'i phyag-chen rtsa-ba rgyal-ba'i gzhung-lam) and its auto commentary (the Yang gsal sgron me, "Lamp re-illuminating Mahamudra"), which is still widely taught and commented upon.